The arrangement of the present invention has been developed primarily for applications involving heavy duty tooling. In cases where metal removal rate must be maintained high, extreme conditions of heat and pressure loading are encountered which must be dealt with efficiently and effectively.
One of the first problems encountered is that of holding the cutting insert securely in the pocket of a tool holder against erratic conditions of load pressure and vibration. At the beginning of a cutting operation, the sudden transition from no load to extreme pressure load on the insert can cause the insert to shift position in the holder and thereby effect the accuracy of the planned cut.
At the end of the cutting operation, the sudden disengagement of the cutting insert from the workpiece causes the pressure load suddenly to be removed from the insert and this sudden change in load can, also, cause the insert to shift and distress any repeatable dimensional accuracy which is essential for most tool holders, especially those used on Numerically Controlled machines, to meet.
During the cutting operation, loads of up to 35,000 pounds may be encountered on the cutting insert which, if the insert is not precisely located and firmly held in the holder to begin with, can also cause shifting of the insert during the cutting operation. It is, therefore, of first importance to provide a tool holder that can precisely and securely seat a cutting insert and then securely hold the cutting insert in location during all phases of the heavy duty cutting operation.
When taking a heavy duty cut, such as described above, the efficiency of removing the metal from a workpiece is, thus, to be maximized. The rate of metal removal rate from a workpiece is, however, only one part of the efficiency factor. When using indexable cutting inserts, there comes a point in time when the cutting edge becomes worn and must be replaced with a fresh cutting edge.
To change a cutting edge, the cutting action must be stopped and the machine operator must index the cutting insert to a new cutting edge or replace the cutting insert altogether if all of the cutting edges thereof have become worn. The time it takes the operator to make this change directly affects the effficiency or metal removal rate of a particular machine.
The operator, having stopped the machine after some very heavy duty cutting, now has the situation that the insert he is about to change or index is extremely hot; in fact, too hot to be handled without gloves, rags, or other protection by the operator. Most gloves and other protection worn by the operator are cumbersome to them and, therefore, any system used for locating and seating a cutting insert in a tool holder, should recognize that a minimum of tools should be used at this point, or that if tools are used, they should be of sufficient size and utility to be used by the operator while using gloves or other protective equipment.
Most of the clamps used in heavy metal cutting today require top clamps above the insert and some type of superstructure on the top face of the insert. It has recently been found that these superstructures may not be desirable in that, as the chip runs across the top face of the insert and strikes the superstructure, a significant back pressure is put on the tool holder and consumes unnecessary horsepower from the machine. Inserts have recently been developed wherein chip control may be had without these power consuming superstructures and, therefore, any positive clamping device which obstructs the top face of the insert is not desirable.
Pin type holders must necessarily be used wherein the upper end of the pin is below the top face of the cutting insert and yet the pin firmly locates and holds the cutting insert in the pocket of the tool holder against the extreme pressure loading of heavy duty cutting.
Most of the pin type holders of the prior art were defective in that the pin type clamps merely held the insert down in the pocket without insuring that the insert was positioned or held back against one side wall of the pocket or the pin type holders mainly held the insert back against a side wall means of the pocket without holding the insert down in the pocket and, therefore, did not prevent fluttering of the insert during extreme conditions.
It is, therefore, an object of the present invention to provide a tool holder having a pin-type clamp that is extremely simple to operate, efficient and fast acting, and while, further, is operable to positively locate the cutting insert down against the bottom wall and back against a side wall of an insert recess pocket while, further, being rigid and strong enough to hold the insert in a fixed location in the holder during the extreme and erratic conditions of load pressure and heat accumulation encountered during a heavy duty cutting operation.
A further object is the provision of a new method of holding a cutting insert in a tool holder pocket which permits rapid indexing or exchanging of the insert.